Control Protocol for Entangled Pair Verification in Quantum Optical Networks

TL;DR

This paper proposes a control protocol for coordinating entangled photon pair distribution in quantum optical networks over IP, analyzing how network latency and quantum noise affect entanglement fidelity and rate.

Contribution

It introduces a novel control protocol leveraging standard IP networks for quantum entanglement distribution, addressing classical-quantum channel coexistence issues.

Findings

Latency impacts entanglement fidelity and rate

Quantum memory decoherence limits entanglement distribution

IP network characteristics influence quantum network performance

Abstract

We consider quantum networks, where entangled photon pairs are distributed using fibre optic links from a centralized source to entangling nodes. The entanglement is then stored (via an entanglement swap) in entangling nodes' quantum memories until used in, e.g., distributed quantum computing, quantum key distribution, quantum sensing, and other applications. Due to the fibre loss, some photons are lost in transmission. Noise in the transmission link and the quantum memory also reduces fidelity. Thus, entangling nodes must keep updated records of photon-pair arrivals to each destination, and their use by the applications. This coordination requires classical information exchange between each entangled node pair. However, the same fibre link may not admit both classical and quantum transmissions, as the classical channels can generate enough noise (i.e., via spontaneous Raman scattering) to make the quantum link unusable. Here, we consider coordinating entanglement distribution using a standard Internet protocol (IP) network instead, and propose a control protocol to enable such. We analyse the increase in latency from transmission over an IP network, together with the effect of photon loss, quantum memory noise and buffer size, to determine the fidelity and rate of entangled pairs. We characterize the relationship between the latency of the non-ideal IP network and the decoherence time of the quantum memories, providing a comparison of promising quantum memory technologies.